Approximately 1,700 kindergarten and first grade children were randomly assigned to one of the following groups: Group I - Rinses once every week in school with a 0.2% sodium fluoride solution. Group III - Ingests once a day in school a sodium fluoride tablet containing 1 mg. of fluoride. Group II - Carries out the regimens for both Group I and Group III. The method of assignment resulted in three comparable groups each containing about 560 children. Participants carry out their assigned treatments in classrooms using the close supervision of a teacher. Treatments will be administered for a minimum of eight and nine years for first grade and kindergarten, respectively. Baseline dental examinations were conducted in September 1981. The prescribed treatments were initiated shortly after the examinations were completed. In September 1982, the second year of the treatment procedures were begun in the classrooms. The first follow-up dental examination will be made in October 1983.